M.S. Cha and Y. Lee
IEEE Trans. Plasma Sci., 40, pp. 3131-3138, (2012)
Electric field, Electrically induced instability, Flame cellularity, Premixed flame propagation, Propagation speedenhancement
The effects of electric fields on outwardly propagating premixed flames
in a constant volume chamber were experimentally investigated. An
electric plug, subjected to high electrical voltages, was used to
generate electric fields inside the chamber. To minimize directional
ionic wind effects, alternating current with frequency of 1 kHz was
employed. Lean and rich fuel/air mixtures for both methane and propane
were tested to investigate various preferential diffusion conditions. As
a result, electrically induced instability showing cracked structure on
the flame surface could be observed. This cracked structure enhanced
flame propagation speed for the initial period of combustion and led to
reduction in flame initiation and overall combustion duration times.
However, by analyzing pressure data, it was found that overall burning
rates are not much affected from the electric field for the pressurized
combustion period. The reduction of overall combustion time is less
sensitive to equivalence ratio for methane/air mixtures, whereas the
results demonstrate pronounced effects on a lean mixture for propane.
The improvement of combustion characteristics in lean mixtures will be
beneficial to the design of lean burn engines. Two hypothetical
mechanisms to explain the electrically induced instability were
proposed: 1) ionic wind initiated hydrodynamic instability and 2)
thermodiffusive instability through the modification of transport
property such as mass diffusivity.